Automatic telephone system



-30 Y Aug 1927 G. MARTIN AuTouAT'Ic mawraoma s'is'mu Original Filed June 30- 1920 Re '3 Q Ilgkl FUN Jnuan ur- Patented Aug. 30, 1927. i i 1,640,551

' UNITED STATES'PATENT OFFICE.

minor e. manrm', or cIIIcAeo. ILLm'oIs, assmnon, BY MESNE assronunnrs, 'ro AUTOMATIC ELIIc'raIc Inc, or CHICAGO, ILLINOIS, a oonroiwrrou or DELA- WAR E. J

AUTOMATIC TELEPHONE SYSTEM.

Application filed June 80, 1820, Serial No. 392,943. Renewed June 25, 1926.

My invention relates in general to autoveniently be ten different oflices, and when a matic telephone systems, but is 'more especalling subscriber operates his dial to call a cially concerned with the trunking arrangedesired number, the first digit will operate'a ments in such systems; and .the object of' first selector to select a.trunk line leading 5 the invention may be stated to be, broadly, to the proper office, andthe remaining digits the design of a new and improved trunking will operate second and third selectors and a 00 system for an automatic telephone exchange, connector in the selected ofliceto complete or system, in which connections are estabthe connection. Thus, referring to Fig. 1, lished through the medium of serially resuppose the subscriber at substation A desires lated automatic'switches, and in which one to call the subscriber at substation A. When of the switches in a, series belongingto a the receiver is removed the individual line major group of the systein may be omitted switch or trunk selector C is operated autofor the sake of economy at the initial inmatically to select a trunk line extending to stallation without Interfering with the use an idle first selector, such as the selector D,

15 of a complete numbering system laid out in for example. The calling device is now accordance with the ultimate capacity. operated in accordance with the number of In order to carry out the general ob ect of substation A and when the first digit is the invention-a3 above set forth, I have decalled, the proper office is selected by raising signed a: special selector switch which may the wipers of selector D until they stand op- 20 be called a combination selector and digit posite the level assigned to such office. The

absorber, a digit absorber selector, or simply automatic rotary movement of the selector is a drop back selector. now initiated and atrunk line is selected ex- Thi it h releases drops b k h a tendin to an idle second selector in the discertain digit is .called and in efiect .elimitant o ce, asthe second. selector E, for ex- 5 nates one of the digits in the telephone nump e Then the ng device s pe bers of a certain major group so that the forthe remainin digits, and the selector E, 89 line in such group may b r a h d by ns a third selector, w ich may be the selectorF',

of a smaller series of switches than the lines and a connec or which ma be the connector in other grou s, H are operated successive y to complete the so In view'of the above it will be understood nnection to the desired line.

that the invention resides in the new trunk- The above described trunking arrangell ing arrangement, and in the special means, ment will be recognized as the well known the drop back selector, which-is used to mendecimal or percentage trunking system der this trunking arrangement practicable, which is in use in practically all automatic 3 5 and these features will now be described exchanges. Having paved the way, so to more fully, reference being had to the accomspeak, y describing what is old, I will now panying drawings. proceed to the new features. In laying out In the draw ngs, comprising but a single a telephone system it is desirable to make sheet, Fig. 1 is a'schematic diagram of the the divisionunto offices at the start and to i0 trunkin system; while Fig. 2is an ordinary locate the oflices throu bout the territory circuit iagram of the drop back selector. served in accordance wit the best estimates Referring-to Fig. 1, this diagram shows aof. future growth. It is not meant by this portion of the trunking system in an autothat all offices are necessarily installed at matic telephonesystein having a capacity of once for some sections where a large future 45 100,000 lines, and using the well known growth is probable may not be built up at Strowger vertical and rotary switches operall at the time, or very sparsely; but what ated according to the two wire system of is meant is that an intelligent plan is decontrol. In a system of this size the lines are vised-based .on a study of the probabilities. us uallydistributed among a plurality of dif Those oflioes are installed whichare required ferent offices, and the first selectors, which for immediate needs-and others may be are theswitches which respond to the first reserved for use in sections whichmay be digits in called telephone numbers, may. built up in the future. When such a plan function as oflice selectors. .Since there are is followed certain blocks of telephone numten levels in a selector switch there may conbars. (which of course correspond to the oflices) are set apart for use ineach section, and additionsmay be made from time the 33,000 block of telephone numbers are used.

to time without changin the trunking planb With this arrangement the process of originally adopted or t e telephone numbers ori inally assigned. The desirable feature t at is to be retained at all events, if possible, is that of so arranging the trunking at the start that additions may be installed from time to time without rearrangement of the trunking or changing of tele hone numbers. Heretofore, as far as app icant knows to attain this object it was necessary to install a complete series of switches comprising first, second, and third selectors and connectors in 'each ofiice as soon as such office was started, or initially installed, even though there might be only a few hundred lines served by such olfice at the start. Theselines would have to be .giventhe regular five digit telephone numers in accordance with the general development plan, and this would require the full quota of switches, as stated. 1 j

Now it is quite generally true that when an outlying oflice is first installed it twill serve at the start but a small fraction of its total ultimate capacity. For example, an oifice may be installed to take care of a present total of 500 lines, located in a dis- A trict which, although marked for a large ultimate growth may nevertheless remain below the 1000 line figure for several years. It will be evident that as long as the size of the oflice does not exceed 1000 lines, only second selectors and connectors would be required so far as establishing connections are concerned;'but since as stated, it is de sired to assign five digit telephone numbers at the start, third selectors would ordinarily have to be installed also in order to preserve :the general five digit numbering scheme.

It is. to meet-this situation that I have devised the digit absorber or drop back selec tor. By theuse of this switch, which is used as afirst selector, I am able to omit the third selectors in those oflices where they are not required and still preserve the five digit numbering system. This can be most clearly explained by reference to the drawing, Fig. 1. The u per series of switches comprisin the second selector'F and the connector are assumed to be located in hn oflice having less than 1000 lines connected thereto, and this oflice is accessible from the third level of the ofiice selectors. The first digit inthe telephone numbers of all lines connected to this 'oflice is therefore the digit3;

and the numbers when the oflice is entirely filled up. will run from 30,000 to 39,999. That is, there are ten difierent thousands,

I 30,000, 31,000, 32,000, 33,000, etc., which will v be available ultimatel when thefull quota of switches areinsta ed. For the present,

however, the third selectors are omitted,

establishin a connection between substation A an' A may be explained, the munber of the latter substation being assumed to be 33456. When the receiver is removed the calling line is of course connected with called therefore the selector D is raised to the third level and then immediatelyreleases. When the release takes place a relay is automatically locked up which alters the selector circuit so that if the same digit 3 is "called a second time no release will take place. The calling subscriber now calls the second digit in the number, which is the digit 3, and the selector is again raised to the third-level. This time the switch does not drop back but instead the automatic trunk selecting movement is initiated as usual and an idle trunk is selected which extends to the desired ofiice. This may be the trunk line extending to the second selector F, and when the remaining three digits siderable sum of money at the start and at the same time avoiding the necessity of changing the telephone numbers later on.

When the size of the oilice increases and it finally becomes necessary to give service to more than 1000 lines, the trunking s stem is expanded to full size bythe instal ation of additional switches. These new switches are 'used as second selectors and replace the selectors, such as the selector F, as terminals of the trunk lines coming from the-third level of the first selectors. The present second selectors, such as the selector F, become third selectors and the trunk lines leading thereto will be taken from the third level of the newly' installed second selectors. Then another group of third selectors accessible' from-say the first level of the new second selectors will be installed to take' drop back first selectors amused, and only. The construction of the drop back selecselector. 'Assuming established, the wipers connect with bank contacts 2,3, and 4, and the calling linewill be extended by way of 'stalled all the digits in switch C is operated and normally closed contacts ing relay 11 to the line relay first digit in' ruptions is produced tors makes it possible to change them readily so that whenever the trunking system in an oflice is expanded the drop back feature can be eliminated on the level corresponding to such office. This is of course necessary because with the full number of switches inthe telephone numbers will have to be used. These drop back selectors can best. be understood from a brief description of the operation of one of them in setting up a connection, and such description will now be given, reference being had to the circuit diagram, Fig. 2, which shows" the circuits of the drop back selector D, Fig. 1, in detail. 3

Assuming'that the subscriber at substation A' is callingthe subscriber at substation A, when the receiver is removed the rotary line automatically to estaban idle drop back first further that the selector D is the switch'with which connection is of the line switch will lish connection with 2 and 4, conductors 5 and 7,

of the switch-' 12. Theline relay is accordingly energized over the calling subscribers loop and closes acircuit for the slow acting release relay 13. Upon energizing, relay 13 prepares the selector for operation in its vertical movement at its lower armature, and at its upper armature bank contacts .grounds'the release trunk conductor 6. This latter operation renders the trunk line busy and provides a holding circuit'for the line switch C in the usual and well understood manner. I

The calling subscriber may now operate his calling device in accordance with the the desired number, .which is Asa result a series of interin the circuit'of the line relay 12, and thefsaid relay is deenergized a plurality of times to send a series of impulses through the slow acting relay 15 and the vertical magnet 18. By the operation of the vertical magnet the switch shaft israised stepby step until the wipers 40, 41," and 42 stand opposite'the third level of bank contacts. Relay 15 is energized inseries with the vertical magnet, maintaining. itsarmathe digit 3.

'ture attracted throughout the vertical move- 'ment. and at the third level.

.16, and to circuit is broken.

815,321, March13, 1906, at b in Fig. 3,

engages springs the projection 23 on spring 22 and and 26 are forced into engagement with springs 25 and 27, respectively.

The springs 22 and 24 to 27', inclusive, are

mounted .in any suitable-manneron the upper part of the switch frame in such a position that, the projection on spring 22 will 'be engaged, as stated, by the cup spring casing 21 when the shaft is standing at the Now since the vertical impulses have ceased the slow will deenergize and parallel circuits .wi closed simultaneously 17 and the release magnet 19. Both circuits include the grounded release trunkco'nductor 6, which goes to the rotary vmagnet by way of the contacts of --the stepping relay the release magnet by way 0 the switching springs 25 and 24 andthe upper contacts of relay-14. The rotary ma net' and the release magnet are'accordingly 'oth energized .at .the same time, the former operatter operating for the rotary magnet from the switch shaft. The rotary magnet I also breaks the locking circuit of the stepping relay 16 near the end ofits stroke, and the said. relay is deenergized. This .breaks the rotary magnet circuit and the rotary magnet deenergizes also, with the result that the .switch shaft at once dropsback and re-'- turns to normal position. The restoration of thesh'aft necessarily follows the deener gization of the rotary double dog has been disengaged from the shaft by the release magnet, as previously magnet because thev explained. At the same time that the rotary 1 magnet and release magnet are energized, a circuit is closed byway of springs 27 and 26 for the relay lay 14 locks itself at its lower armature,

breaking its initial energizingcircuit at the same time, and also opens the circuit of the release magnet atits upper armature. Re-. lay 14 is made slightly slow to energize by 14. Upon energizing, re- 1 means of a copper slug so that the release 7 magnet may be The selector D is now in normal position so far as its wipers are concerned, and it will be seen that the net result of thec'alling of the first digit is'the locking up of the re fully energized before, its

as before and the,

circuit of the rotary magnet 17. Now, however, since relay 14 is energized, the circuit of the release magnet is not closed. The rotary magnet is energized to rotate the switch wipers one step into engagement with the firstset of contacts in the third level,

at the same time breaking the circuit of the stepping relay 16. Relay 16 accordingly deenergizes and breaks the circuit of the rotary magnet, which falls back also and again closes its interrupter contact. The

' magnet circuit will again be closed and the switch wipers will berotated another step, the stepping relay and magnet being then deenergized, as before. This operation will continue as long astest wiper 41 engages grounded or busy test contacts. When the test wiper'arrives at a non busy test contact, test contact 44 for example, itwill find no ground potential and the stepping're'la 16 will not again be energized; but instea the switching relay 11,'wh ich has been short circuited heretofore, is energized in series with the said stepping relay over a circuit extending from the grounded release trunk conductorfi by way of the said relay 11, the interrupter'contact of the rotary magnet 17, and the oil normal springs 20 to relay 16. Due to the high resistance of relay 11 relay 16-does not operate. Upon energizing, re- -lay 11 connects the release trunk conductor 6 to the test wiper 41,- and also'extends the line conductors 5 and 7 by way of its upper and lower armatures and their respective working contacts, line wipers 40 and 42, and bank contacts 43 and 45 to trunk conductors 46 and 48.

The trunk line comprising conductors 46, 47, and 48 extends to a second selector, such as the selector F, for example, and when the calling line is connected with this trunk line by the operations above described, the linerelay of such selector is energized over the calling subscribe'rs loop. The line relay closes the circuit of the release relay and the latter closes a holding. circuit by grounding conductor 47, whereby the switching'relay 11 of the selector D and the switching rela of the individual line switch are maintaine energized after the line and release -relaysf12 and 13 have fallen back. c From this point onthe connection is established by operating the selector F and a.

connector such as the connector H responsive to the calling of the last three digits in the desired number. These operations are .well understood and require no further explanation.

It may be stated, in further explanation of the drop back selector, that the-spring assembly comprising the springs 22 and 24 to 27, inclusive, is preferably mounted so that it can be adjusted or shifted up and down in accordance with the level on which it is 'de sired that these springs be operated. This is not absolutely necessary, however. Spring 22 is easily removed, and if at any time it is desired to cut out the drop back'featu're on the level where it is working and change to some other level, the springs corresponding to spring 22 may be removed from all the first selectors and may be replaced by other springs which have the projection located qfurther up or down, as the case may be. It will be understood also that in case there are two oflices operating at the same time without third selectors the first selectors will have an additional set of springs mounted similar to the set described except that they are closed on a different level. The two setsv consider to be new and desire to have protected by Letters Patent will be pointed out.

in the appended claims.

at I claim is:

1. In a telephone system, a subscribers line, a series of switches comprising group selectors, hundreds selectors, and connectors directively controllable by the subscriber on Having described my invention. what I said line for connectin with a second line, a

second series of switc es ce mprising group selectors, thousands selectors, hundreds selectors, and connectors similarly controlled for connecting witha third line, and automatic telephone numbers assigned to said lines all having the same number of digits.-

2. In a telephone system, a subscribers ,whenever the said second line is called in order to cancel one of the digits in the number.

3. In a telephone system, means including a plurality .of serially related directively controlled automatic switches for connecting a calling and called subscribers line, a differant and lesser plurality of similar switches for connecting the said. calling line with another called lme, a uniform numbering. sys-.

'line, a first selector means including said ble-thereto, m'eans including a plurality of ment, a release magnet,

term in which all of the said subscribers have the same number of digits in their telephone numbers,

called line when such switch is first operated in order to cancel one of the digits in the number.

4;. In a telephone system, a selector switch and means for operating the same, said switch having a primary movement'and an automatic secondary .selectin' movement, a slow acting relay energized uring the pri-' mary movement and deenergized on the completion thereof to start the secondary moveand a circuit for said magnet closed by said ,relay .upon -deenergizing in case the primary movement has stopped at a certain predetermined point,

j second line,

5. In a t ephone s stem, V means .inc uding serially related directively. controlled automatic switches for setting up a connection from saidsecond line to said first line,

means including a different number of similar switches for setting up a connection from said first line to said second line, and

' means for operating said switches according lar switches for setting up a. connection from mat-ic trunk a connectlon line, and

I switch and a line-,accessiblethereto,

anycalling line to said second line,tand' accord-- means for operating said switches ing to a uniform. numbering arrangement such that said first line and said second line are both called by means of the samejnumber'of digits. 7. In a telephone system, a first line, asecond line, means including a'plurality of serially related directively controlled automatic trunk" selecting switches for setting up a connection from said second line to said first line, means including a difl'erent; number ofsimilar switches. for setting up a .connection from-said first line to said second means for} operating said switches accordin to a uniforuf numberin arrangement suc that said first line an said secondlineare both called by means of the same number of digits.

8.- In a telephone system, a, connector similarconnector and-a second line accessis'eriall'y related directively controlled autoselecting switches f setting u from any calling line tosai first line .by way of the first mentioned conand means for releasing one of the switches used in calling the said second a first line, a a plurality of another nector, means including a difierent number of similar switches for setting up a connec- 2 tion from any calling line by way of the second mentioned connector, and means for operating said switches according to a uniform numbering line to said second.

arrangement such that said first line and said second line are-both called by means of the same number of digits.

9. In a telephone system, a plurality 01 lines, a plurality of eluding a plurality of serially related directively controlled automatic switches for setting up a connection from any calling line in either ofs'aid pluralities to any line of the first mentioned plurality of lines, means including a smaller number of similar switches for setting up a connection from any calling line in either of said pluralities to any line of said plurality ofother lines, and means for operating said switches according to "a uniform numbering system such other lines, means 1n-' that both called lines are called by means of the same number of'digits. 7

10. In a telephone system, two exchanges, means including a plurality of vserially related directively controlled automatic switches for connecting a calling line in either exchange with a called line in the first exchange, means including a smaller number of slmllar switches for connecting a calling line in either. exchange with a called line in the second exchange, and means for operating said switches according to a uniform numbering arrangement such that the lines inone exchange are called by means of the same number of digits as the lines in the other'exchange.

, 11. In a telephone .system, line, a first selector, means including said first selector', a second selector, and a con a subscribers nector directively controllable by the subscriber on said line tor, another second selector, a third selector,

and anotherconnector similarly controlled telephone.

.in said first selector for automatically cancelling one of the digits in the number whenever'said second line is called.

12. In a telephone system,' 'means includfor connecting with a v second lme, means including said first selecing a plurality of serially related directively controlled automatic switches for connecting a calling and a called'subscribers line, a different and lesser. plurality of similar switches for connecting the said calling line with another called line, a uniform numbering system in'which all of the said subscribers have the same number of digits in their telephone numbers, and means in one of the switches used in calling the said second called line for cancelling one of the digits in the number thereof.

13. In a telephone system, means including a plurality of 'seri lly related directively controlled automatic switches for connecting a calling and a called subscribers line,

said plurality of switches including a firstselector having a single set of wipers, a different and lesser plurality of simllar switches for connecting the said calhng line with an- .other called line, a uniform numbering system in which all of the said subscribers have the same number of digits in their telephone numbers, and means in the first selector used in calling the said second called line for cancelling one of the digits in the number thereof.

14. In a telephone system, means including a plurality of serially related directively controlled automatic switches for connecting a callin and a called line, said series including a plurality of selectors and a connector, each of said selectors having a single set. of wipers, a second series of similar switches for connecting the said calling line with another called line, the said second series including a smaller number of selectors than said first series, a uniform numbering system in which all of the said subscribers have the same number of digits in their telephone numbers, and means in one of the select-ors used in calling the said second calledlline for cancelling one of the digits in the number thereof.

; In a telephone system, a'selector switch and, means for operating the same, saidswitchhaving a directive primary movement I and an automatic secondary selecting movement, means normally eflt'ective to start the secondary movement at the end of the primary movement, a release magnet, and adjustable means responsive to the primary movement but eflective only at the end thereof for closing acircuit for said release magnet in case the primary movement has stopped at a predetermined point, whereby .said switch can be caused to restore at the end of a primarymovement of any desired extent.

16. In a telephone system, a switch having a wiper, levels of trunk line terminals of two numerical orders accessible from the said wiper, means for operating the switch in correspondence with the numerical orders, respectively, to select a trunk line of a corresponding numerical order level, and means for barring the switch from seizing a trunk of a selected level of one of said numerical orders if the switch has been selectively operated with respect to such level inaccord-Q ance with the other numerical order.

17. In a telephone ,system, a switch, a

group of trunks accessible to the wiperskof said switch and extending to thousands se-.

extending to hundreds selectors, means for operating the switch in accordance with the thousands and hundreds digits of telephone 'lectors, a second group of trunk lines accessible to said switch via the same wipers and.

numbers to select said groups, respectively,

and means e-flective to prevent the seizure of a trunk line in case said switch 1s operated to select the group of trunk lines leading to hundreds selectors responsive to the thousands digit of a number.

j 18. In a telephone system, an automatic switch, two groups of trunk lines terminating in the bank of said. switch, means normally efi'ective to bar access to one of said groups of trunk lines, and means in said switch responsive to a predetermined directive movement thereof for rendering the said group of trunk lines accessible to said switch while also maintaining the other group of 

